1. Field of Invention
The invention relates to the field of reading, writing, inspecting, printing, engraving, plotting, and vision. In the reading aspect it particularly relates to the fields of machine vision and inspection machines, such as those used to read and/or inspect industrial products such as compact disks (CDs), computer disks, video disks, digital video disks (DVDs), Printed Circuit Boards (PCBs) and silicon wafers used in the integrated circuits (IC) industry. In the printing aspect it relates to the field of writing, engraving, and printing machines, such as those used in the industrial fields of digital printing, internal drum scanning, preprinting and pre-press industry, laser beam writing, and photolithography.
2. Prior Art
Conventional scanners which use external drum scanning, such as scanner 1 of FIG. 1, includes a rotating drum 2, which carries a flexible plate 4 on its circumference and a read-write head 6 having a focusing lens 7 that emits and collects multiple beams 8 onto and from plate 4. While drum 2 rotates around its axis 10, head 6 moves parallel to axis 10 and along arrows 12 and 14 and thus the whole area of plate 4 is scanned.
FIG. 2 illustrates an internal drum scanner 19 including a flexible plate 20 bent into cylinder-like shape, a spinning tilted mirror 22, and a head 24 having a focusing lens 25 that emits and collects a single beam 26 onto and from plate 20. The optical path between plate 20 and head 24 includes mirror 22. Mirror 22 spins around its axis 28, along which beam 26 propagates between mirror 22 and head 24. Mirror 22 and head 24 both move along and parallel to axis 28 along a rail 30 and thus scan the whole area of plate 20.
External scanner 1 of FIG. 1 has the advantages of using multiple beams 8 and head 6 with its focusing lens 7 that is close to plate 4. These advantages allow multiple scans at high resolution. The disadvantage is the mechanical instability of its large rotating drum 2 that carries plate 4. This disadvantage forces the use of a low rotational speed.
The advantage of internal scanner 19 of FIG. 2 is the compact size of its spinning mirror 22 that allows it to spin at a very high rotational speed. The disadvantage is the relatively long optical path between its head 24 and its plate 20 via mirror 22. This requires that lens 25 have a long focal length that provides only limited resolution.
The scan speed V of the scanner is proportional to the product of the number N of beams used, times the rotational speed, xcfx89, i.e.,
Vxe2x88x9dNxc2x7xcfx89
The typical values of the above parameters for external scanning are N=30 and xcfx89=500 rpm. Thus V is proportional to 15,000. The typical values of the above parameters for internal scanning are N=1 and xcfx89=15,000 rpm. Thus V is also proportional to 15,000.
It can be seen that both scanner 1 and scanner 19 have a similar scan speed V, but scanner 1 is superior to scanner 19 due to its high resolution.
U.S. Pat. No. 5,557,438 to N. Schwartz and A. Shahar, entitled xe2x80x9cScanning And Tracking Using Rotating Polygonsxe2x80x9d, Sep. 17, 1996, discloses a unique scan system using polygonal mirrors. This system teaches how to convert a scanner 19 into an internal scanner that is capable of scanning multiple beams while maintaining the high performance of scanner 19. In this scanner, if the typical number N of beams is 10, then the scan speed V is proportional to 2xc2x710xc2x715,000=300,000, which is 20 times faster than scanner 1. While the scan speed is much faster, its resolution is still similar to the resolution of scanner 19, which is inferior to the resolution of scanner 1.
U.S. Pat. No. 5,828,483 to A. Shahar and N. Schwartz, entitled xe2x80x9cPrinting And Inspection System Using Rotating Polygon And Optical Fibersxe2x80x9d, Oct. 27, 1998, teaches how to convert internal scanning into wide planar scanning. In this system radiation is projected and collected onto and from a planar region by the outputs of the optical fibers. This system also suffers from the disadvantage of limited resolution.
Accordingly several objects and advantages of the invention are as follows:
(1) To provide an improved scan system.
(2) To provide writing and reading scanners for internal drum scanning which are capable of maintaining all the high performance of the system of the above ""438 patent, with the additional advantage of high scan resolution.
(3) To provide writing and reading scanners for planar scanning which maintain all the high performance of the scanner of the above ""483 patent, with the additional advantage of high scan resolution.
Other objects and advantages are:
(4) To provide disk drivers using multiple beams for fast reading of CDs, computer disks, video disks and DVDs.
(5) To provide inspection systems using multiple beams for fast inspection of CDs, computer disks, videodisks and DVDs.
(6) To provide writing machines using multiple beams, such as writing machines for fast writing and engraving of CDs, computer disks, videodisks, and DVDs.
(7) To provide writing, laser writing, photolithography, and reading or inspecting systems using multiple beams, especially such systems for reading or inspecting PCBs.
(8) To provide writing, laser writing, photolithography, and reading or inspecting systems using multiple beams, especially for reading or inspecting wafers, such as silicon wafers used in the IC industry.
(9) To provide an internal drum scanner and planar scanner using at least one radiation beam for fast reading and writing with high resolution and for inspection by imaging and laser scattering.
(10) To provide internal drum and planar scanning at angular velocities that are equal to or twice the rotational speed of the scan device.
(11) To provide a rotating confocal microscope for reading, inspecting, and writing by inner drum scanning and planar scanning.
Still further objects and advantages will become apparent from a consideration of the ensuing description and accompanying drawings.